To determine a porosity of a subterranean formation, it may be desirable to make several simultaneous measurements. One tool for measuring porosity is based on neutron transport through the subterranean formation. The neutron flux attenuated with distance from the source may depend strongly on the hydrogen content of the subterranean formation. For a neutron source, radioactive chemical sources or accelerator based sources are used in existing tools.
If pore spaces are filled by liquid, the higher porosity corresponds to a higher hydrogen index. The detected neutron counts are generally lower in this case. A properly calibrated tool may increase the accuracy of the porosity measurement in liquid-filled formations if the matrix composition is known. However, the measurement may be affected by various environmental conditions.
On the other hand, the same measurement may be less accurate for gas-filled subterranean formations when the hydrogen content in the pore spaces is lower due to the relatively low density of the gas. A density measurement may address this ambiguity. For the same porosity of the subterranean formation, the gas-filled and liquid-filled matrices have different densities.
A charged particle accelerator may include multiple electrodes at different potentials. To charge the electrodes, a voltage source may be used. The voltage source is coupled to a voltage divider, and different outputs of the voltage divider are in turn coupled to different electrodes. Currently, such a voltage divider is constructed by soldering resistors onto conductive traces on a housing of the electron accelerator.